RU2222829C2 - Use of inorganic particles and method for marking and identifying substratum or part - Google Patents

Abstract

FIELD: marking objects, especially securities. SUBSTANCE: use is made of marking means in carrier medium in the form of at least one inorganic particle including minimum two chemical elements in at least one preset proportion of elements, this proportion being used as code or part of code in which particle is chosen from group of non-stoichiometric crystals; particle remains in carrier medium for in-situ determination of preset proportion of elements. As soon as this marking means is obtained, its inorganic particles are introduced in carrier which is, essentially, cover compound, best of all ink, and this cover compound is applied to part to serve as marking. For identification position of these particles is located by using analytical method, preferably by scanning electronic microscopy and proportion of chemical elements in particle composition is found, best way of doing so being X-ray dissipation with respect to energy or wavelength on scanning electronic microscope. EFFECT: enlarged functional capabilities and noise immunity. 24 cl, 8 dwg

Description

FIELD OF THE INVENTION
The present invention relates to the use of inorganic particles that contain at least two chemical elements in a predetermined and analytically identifiable ratio, to a method for labeling a substrate and to a method for marking and identifying a substrate and / or product.

 The present invention can be used in the encoding of products and documents.

State of the art
Coded microparticles, the code of which is represented by at least three visually distinguishable colored layers of organic resins, and their use as a mark and / or security element in order to prevent counterfeiting of products, have already been described in German patent DE 2651528 and US patent 4329393. Initially these particles were designed to track explosives from production to explosion. These tags were sold under the trademark Microtaggant or Microtrace.

 Since the only characteristic of coding is the color sequence of the layers, the use of these labels is limited by particle size and material choice. Particles smaller than 30 microns are a requirement for many applications, in particular in printing inks and related products. It is difficult to obtain high resolution lines and numbers with printing inks that contain particles larger than the printed element itself. Particles made from an organic laminate can hardly be crushed to sizes in the desired range. An additional disadvantage of these organic particles is the lack of thermal stability. This leads to the destruction of the marking or security element when the product is exposed to fire or heat.

US Pat. No. 5,670,239 describes a composition for delocalized product labeling that makes it difficult to counterfeit or misuse these products. This composition contains non-traditional chemical elements, that is, more or less rare elements from the main groups and subgroups of the Periodic system of elements. In particular these are elements which have a K _α line in the X-ray spectrum in the range between 3.69 and 76.315 keV and which may be present either in elemental form or in the form of any desired compound.

 The elemental composition and concentration of the elements serve as information stored delocalized, which cannot be recognized with the naked eye. An information element, for example, an encrypted digital code or an alphanumeric combination, can be represented by a set of specific elements or compounds, where each particular element or connection is a code symbol, and the concentration of the element or connection expresses the value of that symbol, for example, a number or letter. If a specific element or compound related to this set is absent in the composition, then the value of the corresponding symbol is zero or this symbol is absent.

 US Pat. No. 5,670,239 has some disadvantages. In this marking method, in any case, the search for exact concentrations is required for marking the components of the composition in the mass of marked materials, coatings or ink for printing. This depends on the uniform distribution of the marking components, which are usually provided as a solution. The selection of compounds of all the desired elements that homogeneously dissolve in the coating composition in the entire required concentration range without the formation of a precipitate is very difficult.

 In addition, the use of mixtures of materials in the solid state is excluded due to their inherent tendency to segregation in accordance with particle size, specific gravity, etc.

An additional disadvantage is the limited range of coding capabilities, since each particular chemical element or substance can only represent an n-significant code element. Therefore, the total encoding capacity for m specific elements is determined by the expression n ^m . The limited coding capacity is due to the fact that only chemical information is evaluated in a delocalized coding system. Thus, the code can be opened using any sufficiently sensitive analytical method in which quantitative information can be obtained, that is, classical elemental analysis, X-ray fluorescence, laser-ablation mass spectrometry with induced plasma, etc. This facilitates the decoding and reconstruction of the code by any potential forger.

 An additional disadvantage of the recommendations of US patent 5670239 is the sensitivity of encryption to disturbing elements. One or more elements used for encryption may be accidentally present, for other reasons, in the marked object or on its surface. This will prevent proper reading of the encoded character. Conversely, indignation of other security systems may arise due to the presence of this type of coding, in particular, if soluble compounds of rare earth ions are used, which often luminesce in the visible or infrared region of the spectrum. This type of interference is probably observed for security documents, which require a combination of multiple security systems.

 Therefore, the aim of the present invention is to provide a marking tool, in which there are no disadvantages of the prior art and which are particularly suitable for use in security documents.

 The purpose of this invention is also the provision of a judicial tool for marking products that protects against tampering or inappropriate use.

 The aim of the present invention is also to provide a marking means that is compatible with existing security systems, especially those used in security documents and which serve to recognize these documents in automatic devices.

 The aim of this invention is also to increase the encoding capacity.

 The aim of this invention is also the provision of encryption, which makes it difficult to recreate the marking and which cannot be destroyed by most public analytical instruments.

 The aim of this invention is also the development of a means of marking, which does not depend on the formation of homogeneous mixtures with substrate material, or product materials, or with ink for coating or printing, which are used for marking.

 These goals can be achieved using features of the independent claims.

 In particular, these goals were achieved by using at least one type of inorganic particles containing at least two chemical elements in a predetermined and analytically identifiable ratio as a marking agent.

 These particles are introduced inside or applied to the product as a marking agent. The specific ratio of elements in this inorganic particle, which is characteristic for each type of particle, is a code or part of a code.

 Particles containing information can be localized by scanning electron microscopy (SEM) using backscattering electron detection.

Thus, the centers, that is, the particles in which the information is contained, must be localized in the first stage. After localization of the particles containing information, it is possible to determine the ratio of the chemical elements contained in this particle by analyzing the scattering of x-ray radiation by energy or wavelength (RRE). Both stages, i.e. particle localization and analysis are carried out on the same equipment - a scanning electron microscope. Proper label decoding according to the present invention is associated with analytical methods that combine both microscopy for localization and elementary analysis for reading code. When concentrating encoded information to at least one localized particle, the search for information does not depend on the homogeneity of mixing. For reading such marking, the most convenient method is currently SEM / RRE. In the SEM / REE method, a particle volume of the order of 0.01 μm ³ is sufficient for proper reading.

 An additional advantageous feature of the SEM / RRE analytical method is its dependence on standards in order to obtain reliable quantitative results. The amount of element present in the particle is determined by the intensity of its characteristic x-ray emission. However, this emission depends on the given excitation conditions, i.e., the energy of the exciting electron beam. Since the energy of the exciting beam is more or less attenuated depending on the density of the material, it is necessary to analyze with respect to standard materials of a similar chemical nature. In the absence of such standards, quantitative results may be completely wrong. In applications for security documents, standards and their exact composition are known to the owner of the marking, but not to the forger. Therefore, the forger must rely on indirect data and therefore it will be impossible for him to copy the marking, even if he has at his disposal the SEM / RRE equipment and the possibility of synthesizing materials.

 Marking particles can contain any chemical element.

 Particularly effective are the elements of the second part of the Periodic Table, since the particle localization in a scanning electron microscope is facilitated for them. However, for coding purposes, any element with an atomic number of at least 5 can be used. These elements can be detected using the detection and analysis devices mentioned above.

The coding compounds used in the present invention are preferably selected from non-stoichiometric crystalline compounds or glasses of various types. However, not quite with the same potential for protective ability, stoichiometric crystalline compounds are satisfactory for some applications. Stoichiometric compounds are those compounds that can exist only with a certain ratio of elements. Examples of stoichiometric compounds are calcium carbonate (CaCO ₃ ), quartz (SiO ₂ ), barite (BaSO ₄ ), etc.

 Non-stoichiometric crystals are solids with a microscopically ordered structure, i.e. their atoms are arranged in a regular manner, which is called the crystalline structure. In some crystalline structures, substitutions of atoms of one type for others are quite acceptable without the necessary change in their microscopic order, provided that certain general rules are observed, such as the size of atoms and electrical neutrality.

Examples of these types of structures are spinels (AB ₂ O ₄ ), garnets (A ₃ B ₂ C ₃ O ₁₂ or A ₃ B ₅ O ₁₂ ), perovskites (ABO ₃ ), lanthanide oxysulfides (Y, L _n ) ₂ O ₂ S , zircons (ABO ₄ ) and others. Here A, B, C mean different types of centers that occur in the crystalline structure; these centers should be occupied by the corresponding metal ions. Lanthanum (Ln) is an element from a number of lanthanides, i.e. elements from 57 to 71. In all these structures, this center can be occupied either by one type of metal ion, or by a mixture of various types of chemically similar metal ions. For example, all compounds Fe ₃ O ₄ , ZnFe ₂ O ₄ , (Zn _x Co _1-x ) Fe ₂ O ₄ and Co (Fe _2-x Al _x ) O ₄ have a spinel structure. The parameter x in some of these formulas can be chosen arbitrarily, i.e. there is one or more concentration ratios that are not prescribed by stoichiometric considerations. The present invention reliably relies on the existence of this type of compounds in the implementation of suitable particles containing information.

Glasses are solid materials that are characterized by a lack of microscopic order. At the atomic level, the structure of glass resembles that of a liquid. Glass can be thought of as a very viscous liquid at room temperature. The composition of the glass can vary significantly, and you can enter (dissolve) a large number of additional metal ions in the base material that forms the glass. Such glass-forming substances are known compounds in the field of oxides (B ₂ O ₃ , SiO ₂ , etc.), fluorides (BeF ₂ , etc.), nitrides, etc. By definition, the composition of the glasses is non-stoichiometric, since they have there is no crystalline structure according to which their stoichiometry can be determined. The only limiting factor in glass formation is solubility, i.e. the ability of all desired components to mix homogeneously in a single melt and remain in solution upon cooling. To achieve the objectives of the present invention, very unusual glasses can be prepared, for example, glasses containing Si, Ge, Al, La, Ta, Er and O at different ratios of these elements. Glasses can be crushed to particles of the desired size, although such grinding requires an improved technology if it is necessary to obtain very fine particles of the order of 3-5 microns.

 In another embodiment, these particles are an alloy of metals, such as aluminum-nickel-cobalt, brass, bronze, etc.

 All types of particles can be used either individually or in any desired combination.

 One embodiment of the present invention is that the particle containing the information consists of overlapping layers that contain chemical elements in a non-stoichiometric or stoichiometric ratio.

Inorganic particles can be of any shape, including particles of irregular as well as regular shape. The size of such particles is practically in the range between 0.1 and 30 microns, preferably in the range between 0.5 and 10 microns, and even more preferably in the range between 1 and 5 microns. The term "practically" means that 80% or more of the total weight of the material falls within this range. The volume of individual particles practically lies in the range between 0.01 and 10,000 microns ³ , preferably in the range between 0.1 and 1,000 microns ³ , more preferably in the range between 1 and 100 microns ³ .

 The inorganic particles of the present invention can be mixed into the medium of any carrier that is capable of forming stable dispersions of these particles and holding these particles in place of their localization and analysis. Preferably, these particles are mixed into any type of coating composition and printing ink that is applied to any type of substrate to be labeled. In a preferred embodiment, if the encoding is to remain invisible to the human eye, then the medium of the carrier forming the film is chosen so that it is transparent in the visible region of the electromagnetic spectrum. In an additional embodiment, the application of the particles is introduced into the volume of the material, which then give the desired shape by extrusion, casting, molding, casting, rolling, etc. Coating compositions or printing inks containing such particles can be applied to the support substrate in any known manner. These methods include spraying, brushing, dipping, printing. Printing can be performed as intaglio printing, engraving, offset printing, silk-screen printing, letterpress, flexography and similar methods.

 Particles containing information can also be introduced into compositions covering powder, toners, etc., as well as into paper, security document foil, plastic sheets and fiber, in particular for securities, banknotes, checks, etc., and for security documents, passports, driver’s licenses, etc. Moreover, they can be used in credit cards, identification cards, access cards and all other types of cards related to rights or having value.

 The effective amount of particles necessary for reliable detection and analysis ranges from 0.0001 to 10 wt.%, Preferably from 0.001 to 1 wt.% And even more preferably from 0.01 to 0.1 wt.% Of the total weight composition or material to which the particles are added.

 Counterfeiting protection is enhanced when these particles additionally possess luminescent, magnetic, IR absorbing and resonant (in the radio frequency and / or microwave range) properties. Coating compositions and / or ink for printing can be applied to any security document in order to prevent falsification or unauthorized trade and use of the specified document.

 The reading of the codes according to the present invention can be carried out using any scanning electron microscope currently available, provided that it is equipped with a backscattering electron detector and an X-ray dispersion detector by energy or wavelength. The examples given below were obtained on three different devices (LEO 435VP, Philips XL30W and Hitachi S-3500N), which can be used, without distinction, for the same purpose.

 In scanning electron microscopy, the sample is scanned with a very finely focused electron beam with a spot size of 5 to 10 nm and an electron energy of 1 to 30 keV. When this primary beam hits the sample, various types of secondary radiation arise that can be detected using appropriate instruments. A graph of the intensity of the corresponding detector depending on the coordinates of the scanning electron beam gives an image of a scanning electron microscope. Depending on the electron energy and the density of the sample, the primary beam penetrates the sample to a greater or lesser depth. For example, a beam with an energy of 20 keV penetrates the matrix of organic ink to a depth of about 5 to 8 microns.

The most important types of secondary radiation are:
1. Secondary electrons, ie the electrons of the sample material that are emitted after a collision with the electrons of the primary beam. Secondary electrons have low energy (less than 50 keV) and therefore can only be emitted from the surface layer of the sample. As a result, the detection of secondary electrons gives the topographic appearance of the surface of the sample ("topographic contrast").

 2. Backscattering electrons, ie primary beam electrons that scatter at the nuclei or at the center of the atoms of the sample. Backscattering electrons have high energy close to the energy of the primary beam and can be emitted from the entire volume of the sample into which the beam penetrates. Since the degree of scattering of electrons by an atom increases with an increase in its atomic number, backscattering electrons give the appearance of the chemical nature of the sample ("chemical contrast").

 3. X-ray radiation arising from the re-filling of vacant electron shells in the atoms of a sample after collisions with electrons of the primary ray. Each atom emits a characteristic X-ray spectrum, consisting of lines of K-, L-, M-series, etc., which can be used to conclude the presence of a specific chemical element in the sample, as well as to determine its relative amount, if there is a standard of comparison. The intensity of the obtained x-ray radiation appreciably depends on the energy of the exciting electrons of the primary beam, as well as on the presence of material absorbing x-ray radiation in the path of the beam. As a general rule, the energy of a scanning electron beam should be at least about two times greater than the emission energy of the observed line, and emission lines with an energy value of less than 2 keV will already be distorted by absorption losses in the organic ink matrix. When using a scanning electron microscope, the energy of the primary beam is usually 20 keV. Under these conditions, elements up to bromine (atomic number 35) can preferably be determined on their K lines, while elements from rubidium to bismuth (atomic numbers 37 to 83) should preferably be determined on their L lines. For heavier elements of the latter group, M-lines are also of some interest, and they are preferably used to determine actinides. For the calculation, the peak areas in the series of K-, L- and M-lines are separately integrated and they are taken into account in accordance with the calculation methods that are specific to this device.

 The following drawings and examples may further clarify the present invention, which, however, is not limited to these data.

Brief Description of the Drawings
Figure 1 shows a scanning electron microscope image of a crystalline, non-stoichiometric, inorganic particle of the present invention containing information that is incorporated into gravure printing ink in detecting backscattering electrons (chemical contrast).

 Figure 2 shows the image in a scanning electron microscope of several crystalline, non-stoichiometric, inorganic particles of the present invention containing information in ink for printing by silk-screen printing with variable optical properties.

 In FIG. 3 shows a scanning electron microscope image of the same particles as in FIG. 2 in gravure printing inks with variable optical properties.

 Figure 4 shows the image in a scanning electron microscope of a large mass of crystalline, non-stoichiometric, inorganic particles containing information that is visualized by detecting backscattering electrons.

 In FIG. 5 shows the X-ray energy dispersion spectrum on one of the crystalline, non-stoichiometric, inorganic particles localized in FIG.

 In FIG. 6 shows tabular SEM / RRE data obtained by analyzing inorganic particles according to the invention.

 7 shows a scanning electron microscope image of inorganic particles such as glass containing information in accordance with the present invention.

In FIG. 8 shows an X-ray energy dispersion spectrum in one of the particles of FIG. 7. The chemical composition of the particle is (GeO ₂ —SiO ₂ —La ₂ O ₃ —Er ₂ O ₃ —Ta ₂ O ₅ ).

In FIG. Figures 1–4 show particle localization in an SEM using backscattering electron detection. In this case, the inorganic particles have the composition (Y _{(2-u -vwx)} Nd _u Gd _v Er _w Yb _x ) O ₂ S.

 In FIG. 6 shows tabular SEM / RRE data obtained by analyzing inorganic particles according to the invention. The first column shows the SEM / RRE results that were obtained for the clean particle of Fig. 4 using the internal standardization of the device and algorithms regarding the ratio of elements in a standard particle that will be available only to the owner of the specified standard. Columns 2, 3, and 4 show the SEM / RRE results for each individual label crystal, which are present in concentrations of 1 and 0.1%, respectively, in two different gravure inks. These analyzes were carried out with conventional printing with this ink.

The increased encoding capacity of this type of marking according to the present invention, as well as its insensitivity to disturbing elements and attempts to recreate the code will be illustrated using the following example:
Example
Encoding Particles P1: (Y _1.6 Nd _0.2 Gd _0.2 ) O ₂ S
Coding particles P2: (Y _1.0 Gd _0.2 Yb _0.4 ) O ₂ S
Coding particles P3: (Y _1.3 Nd _0.1 Gd _0.4 Yb _0.2 ) O ₂ S
Camouflage material C1: La ₂ O ₃
Camouflage Material C2: Gd ₂ About ₃
The coding performed by a 1: 1 mixture of particles P1 and P2 can be distinguished according to the present invention from the coding performed by particles P3. In the method of US patent 5670239, these two cases cannot be distinguished. This illustrates the increased coding capacity for the marking means according to the present invention.

The coding carried out with a 1: 1 mixture of particles P1 and camouflage material C1 is easily decoded according to the present invention according to the available element ratio (Y _1.6 Nd _0.2 Gd _0.2 ); Of course, it is enough to localize one crystal of the particle (Y _1.6 Nd _0.2 Gd _0.2 ) O ₂ S and analyze it. Since lanthanum oxide will be further considered in the method of US Pat. No. 5,670,239, it will be included in the total element ratio, in this case (La _1.0 Y _0.8 Nd _0.1 Gd _0.1 ). The compositional ratio obtained by classical elemental analysis, X-ray fluorescence, laser-ablation mass spectrometry with induced plasma, etc. will be the same, which illustrates the increased resistance against reconstitution of the marking agent according to the present invention.

 The above is also true for coding by a mixture of particles P1 and camouflage material C2. Proper code reading is still possible using the SEM / RRE method, while other analytical methods will lead to completely erroneous gadolinium content. This illustrates the resistance of the coding according to the present invention to disturbing elements that may be present for other reasons in the encoded product or on its surface. On the other hand, camouflage material can be added specifically in order to mislead any potential forger.

Claims (24)

1. A marking agent used in a carrier medium and comprising at least one inorganic particle comprising at least two chemical elements in at least one predetermined ratio of elements, this ratio being a code or part of a code in which the particle is selected from the group of non-stoichiometric crystals, and the particle remains in the medium of the carrier for in situ determination of the established ratio of elements. 2. The marking agent according to claim 1, wherein the inorganic particle is selected from the group consisting of non-stoichiometric crystals with the structure of garnet, spinel, perovskite or zircon. 3. The marking agent according to claim 1, wherein the inorganic particle is selected from the group of non-stoichiometric rare earth and / or yttrium oxysulfides. 4. The marking means according to any one of claims 1 to 3, in which the particle volume is from about 0.01 to 10,000 microns ³ , preferably from 0.1 to 1000 microns ³ , more preferably from 1 to 100 microns ³ . 5. The marking agent according to any one of claims 1 to 4, in which the particle is localized by scanning electron microscopy. 6. The marking agent according to any one of claims 1 to 5, in which the inorganic particle is localized in an electron microscope by electron backscattering. 7. The marking tool according to any one of claims 1 to 6, in which the ratio of chemical elements is determined by the method of scattering of x-ray radiation by energy or wavelength using a scanning electron microscope. 8. A marking means according to any one of claims 1 to 7, in which the particle further has one or more of the following properties: luminescence, magnetic properties, IR absorption, radio frequency resonance. 9. A marking agent according to any one of claims 1 to 8 for marking security documents. 10. A carrier, which is a coating composition or printing ink, or material such as paper, security foil, plastic card or fibers, including a marking agent according to any one of claims 1 to 8, in which the predetermined ratio of at least two chemical elements in the particle serves a marking characteristic, the particles being contained in an amount of from 0.0001 to 10%, preferably from 0.001 to 1%, and more preferably from 0.01 to 0.1% of the total weight of the entire coating composition, paint or material to which they are added. 11. A method for marking products, comprising the steps of: (a) obtaining at least one marking agent with an analytically determined characteristic, comprising at least one inorganic particle from non-stoichiometric crystals, containing at least two chemical elements in a predetermined ratio serving as a marking characteristic, wherein this ratio of chemical elements is a code or part of a code; (b) introducing the inorganic particle obtained in stage (a) into a carrier comprising a coating composition, preferably a printing ink; (c) applying a coating composition, preferably the printing ink obtained in step (b), to the product as a marking. 12. The method of marking products according to claim 11, comprising the steps of: (a) obtaining at least one marking agent with an analytically determined characteristic, comprising at least one inorganic particle from non-stoichiometric crystals, containing at least two chemical elements in a predetermined ratio, serving marking characteristic, moreover, this ratio of chemical elements is a code or part of a code; (b) introducing the inorganic particle obtained in stage (a) into a carrier comprising a coating composition, preferably a printing ink; (c) introducing into the carrier obtained in step (b) one or more camouflage compounds containing at least one of the chemical elements that make up the particle in a predetermined ratio; (d) applying a coating composition, preferably the printing ink obtained in step (c), to the product as a marking. 13. The method according to claim 11 or 12, in which the particle is localized on a scanning electron microscope by electron backscattering. 14. The method according to any one of claims 11 to 13, in which the volume of an individual particle is from about 0.01 to 10,000 microns ³ , preferably from 0.1 to 1000 microns ³ , more preferably from 1 to 100 microns ³ . 15. A method for marking and identifying products, comprising the steps of: (a) obtaining at least one marking agent with an analytically determined characteristic, comprising at least one inorganic particle from non-stoichiometric crystals, containing at least two chemical elements in a predetermined ratio, serving as a marking characteristic moreover, this ratio of chemical elements is a code or part of a code; (b) introducing the inorganic particle from step (a) into a carrier comprising a coating composition, preferably a printing ink; (c) applying a coating composition, preferably a printing ink obtained in step (b), to the product as a mark; (d) localizing the position of the particle obtained in stage (a) and located in the applied coating composition or printing ink obtained in stage (b), using an analytical method, preferably scanning electron microscopy; (e) determining the ratio or ratios of the chemical elements that make up the particle localized in step (d), and this determination is preferably carried out by X-ray scattering by energy or wavelength using a scanning electron microscope. 16. The method of marking and identification of products according to clause 15, which includes the steps of: (a) obtaining at least one marking agent with an analytically determined characteristic, comprising at least one inorganic particle from non-stoichiometric crystals, containing at least two chemical elements in a predetermined ratio serving as a marking characteristic, and this ratio of chemical elements is a code or part of a code; (b) introducing the inorganic particle obtained in stage (a) into a carrier comprising a coating composition, preferably a printing ink; (c) introducing into the carrier obtained in step (b) one or more camouflage compounds containing at least one of the chemical elements that make up the particles in step (b) in a predetermined ratio; (d) applying a coating composition, preferably the printing ink obtained in step (c), to the product as a marking; (e) localizing the position of the particle obtained in stage (a) and located in the applied coating composition or printing ink obtained in stage (c) using an analytical method, preferably scanning electron microscopy; (f) determining the ratio or ratios of the chemical elements that make up the particle localized in step (e), and this determination is preferably carried out by X-ray scattering by energy or wavelength using a scanning electron microscope. 17. The method according to clause 15 or 16, in which the particle is localized on a scanning electron microscope by the method of backscattering of electrons. 18. The method according to any one of paragraphs.15-17, in which the volume of an individual particle is from about 0.01 to 10,000 microns ³ , preferably from 0.1 to 1000 microns ³ , more preferably from 1 to 100 microns ³ . 19. A method for marking and identifying products containing material such as plastic, paper, protective foil or fibers, comprising the steps of: (a) obtaining at least one marking agent with an analytically determined characteristic, including at least one inorganic particle from non-stoichiometric crystals, containing no less than two chemical elements in a predetermined ratio serving as a marking characteristic, and this ratio of chemical elements is a code or part of a code; (b) introducing the inorganic particle obtained in step (a) as a marking into a carrier representing at least one of the materials from which the product is made; (c) localizing the position of the particle obtained in stage (a) and located in the carrier obtained in stage (b) using an analytical method, preferably scanning electron microscopy; (d) determining the ratio or ratios of chemical elements in the particle localized in step (c), which determination is preferably carried out by X-ray scattering by energy or wavelength using a scanning electron microscope. 20. The method of marking and identification of products according to claim 19, containing material such as plastic, protective foil or fibers, comprising the steps of: (a) obtaining at least one marking agent with an analytically determined characteristic, comprising at least one inorganic particle from non-stoichiometric crystals, containing at least two chemical elements in a predetermined ratio, serving as a marking characteristic, and this ratio of chemical elements is a code or part of a code; (b) introducing the inorganic particle obtained in step (a) as a marking into a carrier representing at least one of the materials from which the product is made; (c) introducing into the carrier obtained in step (b) one or more camouflage compounds containing at least one of the chemical elements that make up the particle in a predetermined ratio; (d) localizing the position of the particle obtained in stage (a) and located in the carrier obtained in stage (c) using an analytical method, preferably scanning electron microscopy; (e) determining the ratio or ratios of chemical elements in the particle localized in step (d), and this determination is preferably carried out by X-ray scattering by energy or wavelength using a scanning electron microscope. 21. The method according to claim 19 or 20, in which the particle is localized on a scanning electron microscope by electron backscattering. 22. The method according to any one of paragraphs.19-21, in which the volume of an individual particle is from about 0.01 to 10,000 μm ³ , preferably from 0.1 to 1000 μm ³ , more preferably from 1 to 100 μm ³ . 23. A security document, preferably made of paper or plastic, such as banknotes, securities, identification cards, plastic cards or security foil, marked according to the method according to any one of claims 11 to 22. 24. A labeled product, which includes a marking means according to any one of claims 1 to 8 with an analytically determined characteristic, comprising at least one inorganic particle of non-stoichiometric crystals, containing at least two chemical elements in a predetermined ratio, serving as a marking characteristic, this ratio chemical elements is a code or part of a code.

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